Hereditary Hemorrhagic Telangiectasia
What is hereditary hemorrhagic telangiectasia (HHT)? What does HHT look like?
HHT happens when blood vessels in part of the body develop abnormally.
Usually, arteries carry blood into small blood vessels called capillaries. These capillaries then carry the blood into tissue and veins. HHT happens when capillaries do not form normally.
Without capillaries, the blood flows directly into veins at high pressure. This can cause the blood vessels to burst and bleed.
HHT is also known as Osler-Weber-Rendu syndrome.
What are the symptoms of HHT?
The main symptoms of HHT are telangiectasias (tea-langic-TAY-zias) and arteriovenous malformations (AVMs).
Telangiectasias are enlarged blood vessels that look like red lines on the skin. Telangiectasias from HHTs usually happen in these parts of the body:
- Inside of the nose (nasal cavity)
- Skin of the face, hands and mouth
- Lining of the stomach and intestines (gastrointestinal [GI] tract), lungs and brain
AVMs happen when HHT involves larger blood vessels located deeper in the body.
What causes HHT and who gets it?
An abnormal gene causes HHT. It is usually passed down (inherited) from 1 parent who has HHT. Each child of a parent with an HHT gene has a 50% chance of getting this gene from their parent.
HHT is a “dominant” disorder. This means it only takes 1 abnormal copy of the gene, from only 1 parent, to cause the disorder.
It is estimated that 1 in every 5,000 people worldwide has HHT.
What are the signs and symptoms of HHT?
Signs and symptoms include:
- Nosebleeds: Nosebleeds are the most common signs of HHT. About 95% of people with HHT have nosebleeds daily or weekly by the time they reach adulthood.
- Telangiectasias: Enlarged blood vessels that look like red lines on the skin of the hands, face and mouth are found in about 95% of all people with HHT. These do not show up until a person is in their 30s or 40s. Telangiectasias can also bleed, but they are less likely to than those in the nose.
- Stomach or intestinal bleeding: About 25% of people with HHT will develop stomach or intestinal bleeding that can range from mild to severe. Signs of stomach bleeding include vomiting blood or dark, tarry bowel movements.
- Coughing up blood: About 30% of people with HHT have an AVM in the lungs, and some have more than 1. They are marked by coughing up blood. AVMs in the lungs are at risk of rupturing, especially during pregnancy. Someone with a large lung AVM is at significant risk for stroke or brain abscess. Fortunately, lung AVMs are often easily treatable.
- Brain: About 15% of people with HHT will develop brain AVMs. Brain AVMs can be life threatening or disabling if they bleed. With proper diagnosis and screening, most cases can be treated successfully.
Why choose Seattle Children’s Vascular Anomalies Program?
Seattle Children’s Vascular Anomalies Program is one of the best in the nation and 1 of only 2 vascular anomalies programs on the West Coast. Doctors from throughout the Pacific Northwest send children with HHT here for treatment. We see more children with vascular anomalies than any other hospital in the region.
We bring together experts from different specialties to give your child the best possible care. Our vascular anomalies teamincludes otolaryngologists, dermatologists, plastic surgeons, ophthalmologists and interventional radiologists. These doctors work together to develop a treatment plan that fits your child’s unique needs.
We also work with experts in psychology, social work, physical therapy, pain medicine and occupational therapy to meet your child’s medical, social and emotional needs.
How will Seattle Children's diagnose HHT?
We first look at your child’s family history to diagnose HHT. If 1 of your child’s parents has HHT, we carefully monitor your child’s health. Your child should be screened with pulse oximetry every 2 or 3 years to check for AVMs that might affect their heart.
Seattle Children’s is one of only a few centers in the United States providing genetic testing for HHT. We can help you decide if this genetic test is right for your family.
How will Seattle Children's treat HHT?
Treatment for a telangiectasia or AVM related to HHT depends on its size and location.
Most telangiectasias or AVMs should be treated if they:
- Cause a problem, such as frequent nosebleeds
- Have a high risk of causing more severe problems, such as stroke
- Are in the lung or brain
- Laser therapy for telangiectasias of the nose or skin.
- Embolization is a minimally invasive procedure where doctors block blood vessels so blood can’t flow through them. Embolization can fix lung AVMs permanently.
- Brain AVMs are treated in different ways depending on the size, structure and location. Surgery, embolization and stereotactic radiosurgery can all be used, separately or in combination, to successfully treat brain AVMs.
Bleeding from the stomach or intestines is generally treated only if it causes anemia. Anemia is when a child has an unusually low number of red blood cells. These cells carry oxygen to the body’s tissues. Iron replacement therapy is the initial treatment for anemia.